Roundworms

Cat Care > Cat Parasites > Internal Parasites > Roundworms

Roundworms are a white or greyish color and usually about 5 to 15 centimeters in length. Roundworms often appear to be looped or coiled and may change to a pinkish color if they have recently absorbed food. Several worms may occur together as a tangled mass. The most common species to inhabit cats is called Toxocara cati.

An adult worm inhabits the intestine of the cat and, occasionally, a whole parasite may be vomited up or passed out in faeces. The mature worm produces numerous minute eggs that are too small to be seen by the naked eye, and these are passed out with faeces. The eggs have a sticky surface and may adhere to the fur of the cat and be licked up and swallowed during grooming. People can get the eggs onto their fingers when handling and petting the cat. Eggs can persist for a very long time on infected ground and are extremely resistant to decay and pose a potential health risk to very young children. Each egg contains a larva that has the potential to develop into an adult worm but can do this only if it is swallowed by a cat. If ingested by other mammals, such as mice, larvae hatch from the eggs and are carried around the body in the bloodstream. They lodge in various tissues and organs and form a dormant cyst. If eggs are swallowed by a cat, the same migration of larvae, via the bloodstream, occurs through tissues and organs, including the heart, muscles, liver and lungs. Larvae in the lungs may be coughed up into the mouth and swallowed once again.

In adult female cats, some larvae become lodged in the tissues and remain as cysts, causing no further harm. Other larvae return to the intestine and develop into adult worms producing more eggs, but these are safely and effectively eliminated by worming with a suitable drug. A veterinary surgeon can advise on the type of preparation and frequency of use. A cat may be infected directly by swallowing eggs or, quite commonly, by eating encysted larvae present in the tissues of prey animals such as mice and rabbits. Roundworms do not usually cause any problems in adult cats.

Particular circumstances apply to a pregnant queen cat and to young kittens, and worming is vital at this time to reduce the level of infestation. During pregnancy, encysted larvae present in the tissues of the female cat become active and enter the mammary glands. They are passed to the suckling kittens in their mother's milk so that two or three weeks after birth there can be a severe infestation. Kittens with a severe infestation of roundworms can become quite ill. Symptoms include a potbellied appearance, failure to thrive, diarrhea and a dull coat. Larvae in the lungs may cause coughing and noisy breathing. The only way to deal with roundworms is by repeated regular worming of both the queen and her kittens, before and after birth. A veterinary surgeon can advise on the most suitable preparation to use and on frequency of worming.

It is necessary to be vigilant about the elimination of roundworms, not only for the sake of the cat but also because of a potential danger to human health. Those most at risk are very young children who may pick up the eggs on their fingers while playing on contaminated ground and transfer them to their mouths. Any ground that has been used by cats should be regarded as suspect since eggs persist long after faeces have decayed. It is evident that kittens are likely to be infected with roundworms, and if young children have access to them then great care must be taken over hygiene.

It is especially important to make sure that children wash their hands thoroughly and scrub beneath their fingernails after handling kittens. Toxocara cati can complete its life cycle only in cats. However, if eggs are swallowed by a child (or other mammal), the larvae hatch and travel in the bloodstream, lodging and encysting in various organs of the body. This condition, called visceral larval migrans, can cause considerable damage to, for example, the lungs, liver and retina of the eye where abnormal granulation tissue, called granuloma, may be produced. Symptoms include muscular pain, fever, skin rash, respiratory problems, vomiting and convulsions, depending upon the organs affected.

Infection can be treated with various drug preparations, e.g. diethylcarbamazine and thiabendazole, but tissue damage may be permanent. It is believed that young children may be at greater risk as their immune system is immature, whereas older children and adults are more resistant to infection. Visceral larval migrans is a serious condition but fortunately it is rare. Also, it is mainly the dog roundworm that has been implicated as the cause, although the involvement of Toxocara cati cannot be ruled out. It is further believed that many young children with access to pets may be infected without showing any signs of ill health. If sensible precautions are followed, there should be little or no risk.

Another species of roundworm, Toxocaris leonina, occurs more rarely in cats and is usually picked up from prey species Toxocaris leonina does not form cysts in the tissues of a cat and is not implicated in human visceral larval migrans.